Help - Replace handset on Tesco Mobile while in contract?

I own a BB 8520 handset on a Tesco Mobile contract. I'm only about 1/4 into the contract but would like to upgrade the handset because even through its a nice handset I want something that is more robust for business use.

I also own a Playbook which I love so would very much like to upgrade the handset.

I do not understand if I can buy a new BB handset and just fit my existing Sim Card and respective tariff. I know I can't swap the sim card into a non BB handset due to the specific tariff requirements, but I am hoping it can just be a straight swap without issue to a better BB.

You could call or visit your cell phone provider and ask them for input on what you could do. I think you can simply buy the upgrade phone you're looking for; but you might have to pay full price. Is there something wrong with your phone? If so, you can always point that out; but they might just give you a loaner phone of the same type. It really depends on your company; and if you would want to spend full price for a new phone. How long is your contract; and when did you buy the phone? Maybe you have a warranty loop hole or return policy that might help! Good luck!